Television method and apparatus



'Ma zs, 1935. H, R DbNLE 2,002,992

TELEVISION METHOD AND APPARATUS Filed April 1; 1932 2 Sheets-Sheet 1 Iiz-1 INVENTOR May 28, 1935. H, P. DONLE I 2,002,992 I 7 TELEVISIONMETHOD AND APPARATUS Filed A ril 1, 1932 2 Sheets-Sheet 2 fzarvZZZZomZeI INVENTOR Patented May 28, 1935 UNITED STATES TELEVISION METHOD ANDAPPARATUS Harold .P. Donle, Meriden Conn assignor to Radio Inventions,Inc., New York, N. Y., a corporation of New York Application April 1,1932; Serial No; 602,539 :9 Claims (Cl.1i786) The present invention isan apparatus forthe transmission and reception of visual images'such astelevision images.

Several methods and types of apparatus have been used to accomplishreception of television images,'but many have had a general disadvantagein that the resulting image possessed a low degree ofbrilliance,necessitating a darkened or semi-darkened roomfor viewing. The methodand apparatus of the present invention provides an image of a brilliancemuch greater "thanco'nv mon through the use of a concentrated light hasreduced the total light which might be'obtained from the source. Themethod and apparatus of my invention, on the other hand permit the use'of a comparatively large light source, 1. e., in the order of inch indiameter, which allows a relatively great amount, of light to beobtained from the source. I My experience indicat-es that there is amaximum or limiting brilliance (i. e., light per-unit area) which may beobtained in a concentrated-source lamp such as one of the ionized neontype,'so that it is desirable to use a light-area consistent'with thatmaximum brilliance and with the amount ofenergy available for operatingthe lamp; 7

The lamp or light source used in theapparatus of my invention fulfillsthis requirement very closely. Since the illumination obtainedfrom alight source is substantially proportional to the area of the source i.e., the square of its diameter, the light source of myapparatus'delivers approximately times as much light as do the lampsused in most'other apparatus.

Further, in the apparatus of this invention, the adjustments of focus orplacing of the op-' tical elements is relatively simple and is notcritical. 3

A disadvantage of many present types of scanners is that the field ofview is not uniformly illuminated, i. e., the corners or"boundaries ofthe image field are of considerably lowerbrilliance than is the center"of the image field. In the apparatus of my invention this defect isentirely overcome, and substantially uniform' illumination is aninherent characteristic of my novel method of scanning.

Anotheradvantage or" the apparatus of my paratus.

invention isthat the size of the apparatus is relatively small, whencompared with present types or" directly viewed scanners providing thesame size of image as does my apparatus.

My invention will be more .fully'understood by reference to the drawingsforming, part of this specification. p Figfb is a front elevation ofapparatus illustrating thy-invention.

' Fig. 2 is a left-sideelevation of the same appa ratusas' shown in Fig.1.

Fig. 3 isadetailv'iew partially in section of the "means *foraccomplishing vertical framing, as shown in Figs. 1 and 2.

. Referring now toFig. 1, a lamp or light source I I is shown rigidlysupported in a proper position by clamp 12. The light sourceshould bepreferably of a concentrated spot typeand capable of being modulated inbrilliance according to the magnitude of electric current flowingtherethrough. The current may be supplied from any suitable source ofpicture signal, such as a telethrough leads l3 and I 4. The lamp ll mayemit light from crater i 5. a I

The horizontal scanner includes a plurality, of concave cylindricalmirrors 11 which may be attached byany convenient'means to a-drum 18placed in the path of the light fromsource I5 and fixed on a shaft i9carried in bearings 20.

These mirrors may be constructed of silvered" glass, polished metalsheet, or othersuitable ma terial, or may be electroplated" andpolishedon vision receiver, and conducted to the lamp 7 the machinedsurfaces of drum l8. In Figures 1 and 2, the mirrors are assumedto'bemetallic with light rays reflected from their exposed surfaces. Thereflecting surfaces may be positioned upon the drum l8 asshown,with thephysical ing the axis of curvature of the mirror and the axis of thedrum [8.1 The latter construction may be used alternatively for the sakeof slightly modifying the scanning action or of avoiding interfer'encebetween the various optical elements of my apparatus and the variouslight rays which proceed therethrough, in case such interference occursin any modified construction'of'this ap-' Alternatively the drum l8 maybe shaped as a truncated cone, and mirrors I! placed thereabout' sothat'the' axis o'f'curvature of any mirror is contained in a commonplane together with the axis of drum [8 but is not parallel thereto.

ed in a suitable position between lamp il and mirrors IT, in suchmanner. that the axis of curvature of the convex surface of lens lfi (i.e., the central line about which the surface is generated) issubstantially perpendicular to the axes of ourvature of mirrors l1.

The convex cylindrical lens 22 may be support-,; ed in a suitableposition in the path of light from mirrors I? to mirrors 23 in such amanner that theaxis of curvature of the convex surface of lens 22 issubstantially perpendicular to the centers of curvature of mirrors 23.The cross-sectional area of the light path through the lensinay bedelimited by a mask 2| attached to or near the lens and provided with asubstantiallyrectangular opening 2|.

.Themirror drum I8 is driven by an electric motor 29 preferably of thesynchronous type with current supplied from power Yflines 3| throughswitch 32, and with its shaft 30 coupled to the shaft [9 of drum 18through a flexible coupling 28 such as a leather-disc coupling. Motor 29may be mounted in bearings 33 at either end,

' Asegment-sector of a spur gear 134- may be fixed to the motor and meshwith a spurgear- 35 on shaft 35 which carries at its forward endanadjusting vknob SLby which spurgear 35 may be rotated manually. Thisaction may be limited by stops 38 at the upper and lower extremities-ofthe spur gear sector 34, shown in Fig, 1. a

V Thus the frame and field of motor 29 may be rotated over a suitablerange, by this means rotating the drum l8 for the purpose of horizontalframing of the image when the apparatus is in operation. H

The mirror drum 24 is also driven by the sam motor. -A rear extension ofmotor shaft 30 has a worm'44 fixed thereto and meshed with a worm gear45 which may be mechanically connected through a gear train 7 forvertical framing. Sprocket 65. on'shaft 64 is connected by means 25ofdrum 24.

of a chain 74 to a sprocket 21 fixed on the shaft Referring to Fig. 3 acasting 46 is shown with bearings, 41, 48, 49, 50, 5i and 52arrangedtherev in. Worm gear 45 is shown fixed on shaft 53 which may berotatably carried in bearings 49 and 50, and prevented from longitudinalmotion by collars 54 placed at either side of the bearings 49 and 50. Onthe other extremity of shaft 53 may be fixed a spur gear 55 engaging aspur gear 58 fixed on a countershaft 5?, which countershaft may berotatably carried-in bearings 58 arranged at either end of a-' carriage59. 1 Spur gear 56 may engage a spur geared fixed on countershaft 61,which countershaft may be rotatably mounted in bearings 62 incarriage59. Countershafts 5'1 and El may be restrained fromlongitudinaLmotion-bya cover. plate 13 atone end of the carriage 59 anda portion of the fiat side.

of a spurgear 10 at the other end. 1

V Spur gear 60 may engage a spur gear fie fixed on shaft 64, whose axismay coincide with the axis of shaft 53,:andshaft 6411s rotatably carecylindrical lens 22 is 4.0 inches.

ried in bearings 5! and 52. A sprocket 55 on shaft 64 and a collar 66prevent longitudinal motion of shaft 64.

Carriage 59 may be rotatably carried upon coincident shafts 53 and 64 bymeans of bearings 6'! arranged in the carriage, and the rotation of thecarriage may be delimited by means of two stop pins 68 fixed therein onopposite sides of stationary arm 69. A spur gear 18 fixed to the end ofcarriage 59, concentric with shaft 53 engages a spur gear 'H fixed toshaft 43 which may be carried rotatably on bearings ll and 48 withcollars '42 at either side of the bearings. Shaft 43 hasfixed on theopposite end a bevel gear 42 engaging a bevel gear 4| which latter isfixed on control shaft 48 (carried in bearings not shown).

At the other end of control shaft 45, which may be. brought out at thefront of the complete apparatus, an adjusting knob 39 may be fixed, tobe'rotated manually for the purpose of rotating carriage 59. When shaftis rotated the resulting rotation of, carriage 59 and theplanetary gears55 and 60 causes a relative rotation between spur gears 55 and 63, i.e., between motor shaft 30 and sprocket 55. When the carriage 59isstationary, the direction of rotation of spur gear 63 is'opposite tothat of spur gear 55.

It is evident that/when knob 39 is rotated and the angular position ofsprocket 55 is shifted, the angular position of drum 24 is also shifted,resulting in a vertical framing action controlled by the rotation ofknob 39.

Intheoperation of the apparatus of my invention, the number of picturesscanned per second is equal to the number of mirrors 23 on drum 24 Ywhich passacross the field of view in a second. The number of scanninglines per picture is equal to the number ofmirrors H on drum 18 whichpass during the passage of a single mirror 23 on drum24, i.-e., duringthe scanning of a complete picture. The angular speed of drum I8 ispreferably greater than the angular speed of drum 24, so that I shallhereinafter designate them asthe fast drum and slow drum, respectively.The fast drum is shown with 20 mirrors and thslowdrurn with 10 mirrors,so that for scanning 60 lines per picture and 20 pictures per second,the fast drum should revolve 60 R. P. S.

(3600 R. PLM.) and the slow drum should revolve ZR. P. S. (120 R... P.M.) i. e. in angular speed ratio of.v 30:1. Thus the motor 2! revolvesat 3600B. P. M., and the gear train from motor shaft 30 to slow drum 24is arranged fora 30:1 angular speed reduction.

As an example of the construction of the apparatus of my invention, adescription of the approximate dimensions of the apparatus shown inFigs. 1 and 2 will be given. The fast drum l8 shown is 4.2 inches indiameter and 1.5 inches long, while the mirrors if thereon have a radiusof curvature of 1.9 inches. The slow drum 24 shown is 2.95 inches indiameter and- 5.0.inches long, while the mirrors 23 thereon have aradius of curvature-of 1.25 inches. The axis of slow drum 24 is 7.75inches above theaxis of fast drum I8 and is 3.4 inehesbehind thevertical central plane of the fast drum. The equivalent focal length ofthe convex cylindrical lens I5 is 2.0 inches, while theequivalent focallength of the convex The spot source i5 is apprcximately afl inches fromactive mirrors E Land the position of the lenses !6 and 22 maybe easilydetermined from the drawings.

Thehorizontal characteristics of the scanned image may be largelydependent upon the pro:

- mirrors 23.

portions of mirrors II, drum I8. and convexlcylinlight-appear to movehorizontallyin the direction drical -lens.22, as seen in Fig. l-whilethe vertical characteristic of the scanned image may be large.-

ly dependent upon the proportions of,mirrors .23,

drum 2e, and convex cylindrical lens I6, as shown To become familiarwith the optical paths in v the apparatus of my invention it isdesirable to refer to Figs. 1 and 2. As shown intheplane of Fig. 1, thespot of light I5 in lamp i I is projected approximately uniformly overmirrors I'I with- -out experiencing any appreciable deflection by lensIt. Two active mirrors I! are shown reflecting the incident light tofocus in two lines of light 82 and 83 parallel to the axes of curvatureof the mirrors, i. e., perpendicular to the plane of the paper inFig. 1. 8% and S i .of the light so reflected are shown, and

continue their course after passing through tool 82 and 83, to impingeupon cylindrical'convex lens 22 which acts upon the rays in the plane ofFig. 1. After passing through lens 22' the light continuesas if comingfrom image lines of light 83 and 89 substantially parallel to real linesof light 82 and 83, and falls upon two active mirrors -23. horizontaldirection, so that in Fig. lthe light is reflectedfrom mirrors 23 as iffrom planemirrors, to the eye of the observer.

- As shown in theplane of Fig.' 2, the light from the'source spot I5 is'projected upon mirrors I! through convex cylindrical lens It so that inthe passage of light through the lens the rays become more nearlyparallel i. e.','the rays appear 'to come from a virtual image of thesource spot I5 at a greater distance thanisspot I5.

However, the action oflens I6 should not be so great as to cause a realimage of spot I5 to be formed between lens I6 and mirrors H. The lightstriking mirrors I! is refiectedlin the plane of Fig. 2). as if thesewere plane mirrors, and the rays'proceed through lens 22 without anysubstantial deflection, falling upon the two active The boundary rays I02, I33 and H14 of light striking the two active mirrors23 are shown, asare the resulting boundary rays I95, M35, E69 and I II] of the lightafter reflection from mirrors. It is evident that the reflected light isfocused by active mirrors 23 to two lines of light we and I H! which areparallel to the axes of curvature of the mirrors (i. e., perpendicularto the plane of the paper in Fig. 2)} Light rays with boundary anglesI01, and III proceed-from the focal'lines I98 and I I2 into theviewing.area or observers area.

-Since-the pupilof theobservers eye isof limited extent, the light beamenteringi'thereto is likewise of small area, i. e.,'the observers eyereceives only the light reflected from a definite small spot'of point ofan'active mirror 23, and he apparently sees a spot of light upon themirror at that point which apparent spot is effectively an opticalintersection of focal linessuch asIfiS ands-9. When drums l8 and 24arestationary and in the positions 'shown in'Figs. l and 2 an observerproperly situated will perceive four such spotsof light arrangedsubstantially onthe,

four corners of a rectangle. If now the drum I8 is rotated, the spots ofThe boundary rays I8,- l9,

The mirrors 23 act as plane mirrors in the of movement of active mirrorsH, or if the drum 24 is rotated} the light spots appearrto movevertically 'inlthe direction of movement of active mirrors 23,becausethe light entering the eye the area bounded by the four apparentlight spots, and such an area is approximately delimited by the mask-2|, so that when a spot 2I it is not visible to the observer. It ispreferable .thatthe aperture 2I' ofmaskZi be large enough to allowslightly more than one complete imageto be seen, so that observers invarious pomoves'outside the image area delimited by mask sitions shalleach be able to see a complete image.

Whenthe apparatus is in operation and the picture is correctly framed acomplete scanned image. appears, such correct framing being accomplished by rotating shaft 49 to "move the image verticallyandrotating shaft 36 to'move the image horizontally. r

t is evident in. Fig. 2 that the vertical angle :of 'view issubstantially equal to the anglebetween boundary rays I and Ill), Thedefinition of vertical viewing angle. is the vertical angle at thescanner through which the observer may movewhile viewing the entireimage.

The definition of horizontal viewing-angle is similanexcept' that it iswith respect to a movement of the observer through a horizontal angle.It is evident from Fig. 1 that the horizontal'viewing angle issubstantially equal tothe angle between boundary rays. 85 and 86,providedthat drum- His of suihcient length to .40 increasesthe angle ofbrilliance of the image,

Eltherorboth lenses may be omitted or reduced in power at a sacrificeofany one or more of the three iactors'of picturesize, viewing angle,and brilliance, in the dimension afieetedby the lens omitted orweakened.

In Fig. l the width of .the image is equal to the distance D between thevirtual images 8t anddil' of light lines 82 andtil. however, when viewedby the observer, the images-38 and 89 are apparently moved to a positionslightly in front of active mirrors 23 i. e., apparently closer to theobserver than areimages 83 and 89, sothat they appear closer together inthe ratio of L/ (L+Y) where L is-the distance from the observer tomirror 23 and Y is the distance from mirror 23 to images 83 and 83.Finally the apparent width of the image is substantially equal toDL/(L-l-Y). The apparent height of the image (inrFig. 2)issubstantiallyequal'to the vertical distance between image lines m8.and IE2.

From Fig. 1 it is evident that the apparent width of the final imagespot as viewed byflan observer is substantially equal t'ofltheproduct of.(1) the width of the source spot.i5,',,(2) the mag nification by theconcave mirrors ll (which, is

preferably less than unity): (3) the magnification by lens 22 (which isgreater than unity) and (4) theratio oi L/(L-i-Z), where L is thedistance fronithe observer to the active mirrors 23"and Z is thedistance from the active. mirrors 23'to the source spot I5 via theoptical path followed by the active rays. In Fig. 2 it is evident thatthe apparent height of the final image";

spot is substantially equal to-the product of (1)"- the height of thesource spot l5, (2) the magnification by. the convex cylindrical lens I6(which is greater than unity) (3) the magnification by the mirror 23(which .ispreferably much less than unity), and (fl)v the ratio L/L+Xwhere L is the' distance from the observer to the active mirror 23 andX'is the distance from the path followed by the active light rays.

,Thus in the apparatus illustrated in Figs. 1

' and 2, in which the apparent image size, is 1 inches high by 1 incheswide, the source size should be inch high by 1/13 inch wide (orapproximately the area .of a circle inch in diameter) to allow an"overlap of in adjacent scanning lines, i. e., to provide an apparentimage spot .0375 inch square. I

It is apparent therefore, that the size of the light source spot is.considerably greater than the size of the apparent image spot. Asmallauxiliary lens of spherical or cylindrical construction may ofcourse be placed close in. front of light source spot l5 to alter theeffective shape andsize of the spot to any reasonable value, if sodesired. I

Since'there are inthe apparatus no apertures for delimiting anelementary image area, and no 'diifusing screens, the optical efficiencyis very much higher than in a scanner. in which these elements are used.The eifect'in' the apparatusof my invention is that the observer isseeing the light source almost directly, with only an eflicient lens andmirror interposed. I Another advantage of the apparatus of my inventionis that the mirrors and lenses are oper ated at Ya low magnification, sothat optical distortion is negligible, i; e;,--straight lines in thesubject appear as straight lines in the image,e'ven when low gradelenses and mirrors are used.

Another advantage of my, invention isthat the picture is not projectedas a rear image upon a viewing screen, in which the aberration from theentire surfaces of the optical elements would be apparent, but thepicture is viewed directly and the observers eye receives light fromonly a very small area of the surface of any optical element, so thatthe apparent aberration is reduced to a negligible value.

Another advantage-of my invention is that no external picture delimitingmask is necessary be cause the mask between the slow drum and-the fastdrum completely delimits thepicture.

Other modifications of the apparatus disclosed herein will be apparentto those skilled in the art, but do'not affect the novelty of myinvention. For instance, a lens may be positioned between the activemirrors. on the slow drum and. the

observer, for the purpose of magnifying the picture or altering theapparent ratio of its width toits height. shown may be used, such as aseries rheostat and switch in the power supply line to the electricmotoror slipping clutch mechanisms in the mechanical drive system;

The apparatus of FigsQl and 2 may be used for scanning a realsubject'for transmission as, a

' visual image, by'substituting in place of the spot source 15 (in Figs.1 and 2) a photo-sensitive device with appropriate light-admittingaperture.

. If, inthis case, the aberrations of'theoptical ele- Other framingmeans than that,

rors. as described herein may be used in conjunction with other types ofscanners, such as those described in my co-pending applications, SerialNumbers 557,011 and 558,486, the latter now matured as Patent Number1,961,962, by substituting the slow drum of. the present invention forthe slow drum of the existing types of scanners. In the case of theapparatus disclosed in my 00- pending application, Ser. No. 557,011, theground glass screen shown therein should be removed when thissubstitution is made.

An advantage of the substitution in many cases is a resulting reductionin the size of the apparatus needed relative tov the size of the pictureproduced thereby.

Iclaim:

. 1. In an apparatus for scanning a visual image,'a concentrated lightsource capable of modulation, a line scanning device comprisingarotatable element carrying fixed thereon a plurality of concavecylindrical reflectors whose axes of curvature are contained in planescommon to their axis of rotation, and a field scanning device comprisinga rotatable element carrying fixed thereon a plurality of concavecylindrical reflectors whose axes of curvature are contained in planescommon to their axis of rotation, said light source and rotatableelements being arranged to form a scanned image suitable for directviewing by the eye of an observer.

2. In an apparatus for' scanning a visual image, a concentrated lightsource and two rotatrotational axis of their respective supportingdrums. r '3. In an apparatus for scanning a visual 'image, aconcentrated light source, two rotatable drums whose axes aresubstantially mutually perpendicular, each'of. said rotatable drumsbearing upon its cylindrical surface a plurality of concave cylindricalreflectors, a convex cylindrical lens interposed between the lightsource and the first mirror drum, the axis of curvature of saidconvexlens being substantially perpendicular to the axis of said firstdrum, and a second convex cylindrical lens interposed between the firstand second drums, the axis of curvature of said second lens beingsubstantially perpendicular to the axis of said second drum so as toincrease the angle of [direct viewing of the reproduced image. 4.Television scanning apparatus comprising a spot source of light variablein intensity with the received picture signal, a rotating drum havingconcave, reflecting surfaces receiving light from the spot source forscanning in one direction and a second drum having an axis at an angleto'the first drum and having concave reflecting surfaces for scanning ina direction at an angleto the direction of the first scanning, the radiiof curvature'of said reflecting surfaces being such as to produce animage for direct viewing throughout a substantially wide angle of visionand said concavev reflecting surfaces having their majoraxes parallel tothe rotational axes of their respective supporting drums.

5, Television scanning apparatus comprising a, light source'and twodrums for scanning in two different directions arranged with their axessubstantially at right angles to each other, each source and means formoving the point of said drum having a series of concave reflectingsurfaces of such radii of curvature as to produce a directly viewableimage, throughout a wide angle of View and a motor for driving bothdrums in synchronism with the received signal, said reflecting surfaceshaving their major axesparallel to the rotational axes of theirrespective sup porting drums.

6. Means for reproducing television pictures comprising a sourceof-light reflecting means for focusing a bundle of rays from said sourceinto a linear image, first rotating means for moving said image in adirection perpendicular to .its length, separate reflecting means forfocusing said bundle of rays into a second linear image perpendicular tosaid first image, and second rotating means for moving said second imagein a direction perpendicular to its length said first and said secondrotating means revolving about mutually perpendicular axes.

7. In a television reproducer, a source of light, a plurality ofdiscrete reflecting elements for producing in space two virtuallyintersecting and mutually perpendicular linear images or" said virtualintersection so as to scan 'anoptical image, said reflecting elementsbeing substantially at right angles to one another when opticallycooperating. 7

8. In a television reproducer, a source of light, v

means for producing in space two virtually intersecting and mutuallyperpendicular linear true optical images of said source, said linearimages being at materially diiierent optical distances from said source,and means for moving the point 1 a HARoLD P. DONLE.

